Conventional measurement and positioning for linear stage constantly performs mensuration by utilizing a laser interferometer, an optical scale, an autocollimator or an electronic level. However, the mentioned measurement devices are not suitable to install on precise positioning machinery for on-line measurement as a result of heavy overall structure.
Conventional measurement method of the laser interferometer utilizes a way of optical interference to proceed with off-line correction. The procedures of optical interference are: splitting a light beam, making two splitting light beams traveled in two different light paths to reach corresponding reflective mirrors, reflecting the light beams to reach an optical detector by reflective mirrors therefore producing interference pattern through path difference between two traveled light beams, and converting interference pattern into straightness error eventually. However, the laser interferometer is only used for calculating and correcting in off-line mode so the laser interferometer can not satisfy the demand of on-line instantaneous measurement of linear stage.